CCNP實驗:BGP路由黑洞之路由反射器(Router Reflector)解決

【實驗環境】

C3640-IK9O3S-M Version 12.4(10)

【實驗目的】

采用路由反射器(Router Reflector)解決由IBGP水平分割導致的BGP路由黑洞問題

【實驗拓撲】

【實驗描述】

R1、R2、R4、R5跑BGP協議，R2、R3、R4跑OSPF協議。目標是使1.1.1.1<->5.5.5.5可以互相訪問

IBGP鄰居關系采用回環口進行建立

R1<->R2、R4<->R5之間使用直連接口建立EBGP關系

數據層面的BGP路由黑洞問題：由于R3沒有跑BGP，因此R2和R4均不會將路由條目傳給R3，因此R3沒有1.1.1.1和5.5.5.5的路由，導致路由黑洞。如果在R3上跑BGP，與R2和R4建立IBGP關系，又會因為IBGP水平分割導致R2、R4路由學習不完整。

解決方法：利用路由反射器，將R3作為反射器(RR)，其余IBGP路由器作為客戶端(C)，路由反射器和其客戶端共同組成路由反射簇，客戶端只需要與路由反射器建立鄰居即可，不需要與每臺IBGP路由器建立鄰居。

路由反射器的規則：

1、RR從EBGP收到的路由，會反射給客戶端和非客戶端；

2、從客戶端收到的路由，會反射給客戶端、非客戶端及EBGP鄰居；

3、從非客戶端收到的路由，只會反射給客戶端和EBGP鄰居，不會反射給其他非客戶端。

【實驗步驟】

1、R1基本配置，端口:

!
interface Loopback0
ip address 1.1.1.1 255.255.255.0
!
interface Serial0/0
ip address 12.0.0.1 255.255.255.0
clock rate 64000
!

2、R2基本配置，端口，OSPF:

!
interface Loopback0
ip address 2.2.2.2 255.255.255.0
!
interface Serial0/0
ip address 12.0.0.2 255.255.255.0
!
interface Serial0/1
ip address 23.0.0.1 255.255.255.0
clock rate 64000
!
router ospf 110
router-id 2.2.2.2
network 2.2.2.0 0.0.0.255 area 0
network 23.0.0.1 0.0.0.0 area 0
!

3、R3基本配置，端口，OSPF:

!
interface Loopback0
ip address 3.3.3.3 255.255.255.0
!
interface Serial0/0
ip address 34.0.0.1 255.255.255.0
clock rate 64000
!
interface Serial0/1
ip address 23.0.0.2 255.255.255.0
!
router ospf 110
router-id 3.3.3.3
network 3.3.3.0 0.0.0.255 area 0
network 23.0.0.2 0.0.0.0 area 0
network 34.0.0.1 0.0.0.0 area 0
!

4、R4基本配置，端口，OSPF:

!
interface Loopback0
ip address 4.4.4.4 255.255.255.0
!
interface Serial0/0
ip address 34.0.0.2 255.255.255.0
!
interface Serial0/1
ip address 45.0.0.1 255.255.255.0
clock rate 64000
!
router ospf 110
router-id 4.4.4.4
network 4.4.4.0 0.0.0.255 area 0
network 34.0.0.2 0.0.0.0 area 0
!

5、R5基本配置，端口:

!
interface Loopback0
ip address 5.5.5.5 255.255.255.0
!
interface Serial0/1
ip address 45.0.0.2 255.255.255.0
!

6、配置R1與R2之間的EBGP

//R1配置AS 1
router bgp 1
no synchronization
bgp router-id 1.1.1.1
network 1.1.1.0 mask 255.255.255.0
neighbor 12.0.0.2 remote-as 3
no auto-summary

//R2配置AS 3
router bgp 3
no synchronization
bgp router-id 2.2.2.2
neighbor 12.0.0.1 remote-as 1
no auto-summary

7、配置R4與R5之間的EBGP

//R4配置AS 3
router bgp 3
no synchronization
bgp router-id 4.4.4.4
neighbor 45.0.0.2 remote-as 5
no auto-summary

//R5配置AS 5
router bgp 5
no synchronization
bgp router-id 5.5.5.5
network 5.5.5.0 mask 255.255.255.0
neighbor 45.0.0.1 remote-as 3
no auto-summary

8、使用回環接口配置R2、R3、R4之間的IBGP關系

//R3配置
router bgp 3
no synchronization
bgp router-id 3.3.3.3
neighbor 2.2.2.2 remote-as 3
neighbor 2.2.2.2 update-source Loopback0
neighbor 4.4.4.4 remote-as 3
neighbor 4.4.4.4 update-source Loopback0
no auto-summary

//R2配置
router bgp 3
neighbor 3.3.3.3 remote-as 3
neighbor 3.3.3.3 update-source Loopback0
nei 3.3.3.3 next-hop-self

//R4配置
router bgp 3
neighbor 3.3.3.3 remote-as 3
neighbor 3.3.3.3 update-source Loopback0
nei 3.3.3.3 next-hop-self

9、在R3上開啟路由反射器，指定客戶端

router bgp 3
neighbor 2.2.2.2 route-reflector-client
neighbor 4.4.4.4 route-reflector-client

10、查看R3的路由表

R3#sh ip bgp
BGP table version is 3, local router ID is 3.3.3.3
Network          Next Hop            Metric LocPrf Weight Path
*>i1.1.1.0/24       2.2.2.2                  0    100      0 1 i
*>i5.5.5.0/24       4.4.4.4                  0    100      0 5 i

11、驗證R1與R5回環口連通性

R1#ping 5.5.5.5 so 1.1.1.1
Sending 5, 100-byte ICMP Echos to 5.5.5.5, timeout is 2 seconds:
Packet sent with a source address of 1.1.1.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 188/325/496 ms

12、在R2上查看反射路由條目5.5.5.0/24

R2#sh ip bgp 5.5.5.0/24
BGP routing table entry for 5.5.5.0/24, version 3
Paths: (1 available, best #1, table Default-IP-Routing-Table)

4.4.4.4 (metric 129) from 3.3.3.3 (3.3.3.3)
Origin IGP, metric 0, localpref 100, valid, internal, best
Originator: 4.4.4.4, Cluster list: 3.3.3.3

13、在R4上查看反射路由條目1.1.1.0/24

R4#sh ip bgp 1.1.1.0/24
BGP routing table entry for 1.1.1.0/24, version 3
Paths: (1 available, best #1, table Default-IP-Routing-Table)

2.2.2.2 (metric 129) from 3.3.3.3 (3.3.3.3)
Origin IGP, metric 0, localpref 100, valid, internal, best
Originator: 2.2.2.2, Cluster list: 3.3.3.3

14、評價

路由反射器相對于鄰居全互聯來說，簡化了配置和數量，因為IBGP鄰居關系只需要在客戶端與RR之間建立即可。

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